1. Field of the Invention
The present invention relates to an improved method for aspirating emboli, thrombi, and other types of particles from the human arterial or venous system, the method being particularly well suited for treating stenoses or occlusions within saphenous vein grafts, coronary arteries, arteries above the aortic arch such as the carotid and cerebral arteries, and similar vessels.
2. Description of the Related Art
Human blood vessels often become occluded or completely blocked by plaque, thrombi, other deposits, emboli or other substances, which reduce the blood carrying capacity of the vessel. Should the blockage occur at a critical place in the circulatory system, serious and permanent injury, or even death, can occur. To prevent this, some form of medical intervention is usually performed when significant occlusion is detected.
Coronary heart disease is an extremely common disorder in developed countries, and is the leading cause of death in the U.S. Damage to or malfunction of the heart is caused by narrowing or blockage of the coronary arteries (atherosclerosis) that supply blood to the heart. The coronary arteries are first narrowed and may eventually be completely blocked by plaque, and may further be complicated by the formation of thrombi (blood clots) on the roughened surfaces of the plaques. Myocardial infarction can result from atherosclerosis, especially from an occlusive or near occlusive thrombi overlying or adjacent to the atherosclerotic plaque, leading to death of portions of the heart muscle. Thrombi and emboli also often result from myocardial infarction, and these clots can block the coronary arteries, or can migrate further downstream, causing additional complications.
Various types of intervention techniques have been developed which facilitate the reduction or removal of the blockage in the blood vessel, allowing increased blood flow through the vessel. One technique for treating stenosis or occlusion of a blood vessel is balloon angioplasty. A balloon catheter is inserted into the narrowed or blocked area, and the balloon is inflated to expand the constricted area. In many cases, near normal blood flow is restored. It can be difficult, however, to treat plaque deposits and thrombi in the coronary arteries, because the coronary arteries are small, which makes accessing them with commonly used catheters difficult.
Other types of intervention include atherectomy, deployment of stents, introduction of specific medication by infusion, and bypass surgery. Each of these methods are not without the risk of embolism caused by the dislodgement of the blocking material which then moves downstream. In addition, the size of the blocked vessel may limit percutaneous access to the vessel.
In coronary bypass surgery, a more costly and invasive form of intervention, a section of a vein, usually the saphenous vein taken from the leg, is used to form a connection between the aorta and the coronary artery distal to the obstruction. Over time, however, the saphenous vein graft may itself become diseased, stenosed, or occluded, similar to the bypassed vessel. Atherosclerotic plaque in saphenous vein grafts tends to be more friable and less fibrocalcific than its counterpart in native coronary arteries.
Diffusely diseased old saphenous vein grafts with friable atherosclerotic lesions and thrombi have therefore been associated with iatrogenic distal embolic debris. Balloon dilatation of saphenous vein grafts is more likely to produce symptomatic embolization than dilatation of the coronary arteries, not only because of the difference in the plaque but also because vein grafts and their atheromatous plaques are generally larger than the coronary arteries to which they are anastomosed. Once the plaque and thrombi are dislodged from the vein, they can move downstream, completely blocking another portion of the coronary artery and causing myocardial infarction. In fact, coronary embolization as a complication of balloon angioplasty of saphenous vein grafts is higher than that in balloon angioplasty of native coronary arteries. Therefore, balloon angioplasty of vein grafts is performed with the realization that involvement by friable atherosclerosis is likely and that atheroembolization represents a significant risk.
Because of these complications and high recurrence rates, old diffusely diseased saphenous vein grafts have been considered contraindications for angioplasty and atherectomy, severely limiting the options for minimally invasive treatment. However, some diffusely diseased or occluded saphenous vein grafts may be associated with acute ischemic syndromes, necessitating some form of intervention.
There is therefore a need for improved methods of treatment for occluded vessels such as saphenous vein grafts and the smaller coronary arteries, the carotid and cerebral arteries, which decrease the risks to the patient.
The present invention provides a novel method for removing plaque, thrombi, emboli and other types of obstructions or occlusions from blood vessels having an inlet fluid pressure of at least 0.2 psi at any time during the diastolic/systolic cycle of the heart. Although the pressure within the vessel may fall below 0.2 psi during relaxation between heartbeats, so long as the pressure created by the heartbeat rises to at least 0.2 psi, the pressure within the vessel will be sufficient. The method preferably includes the use of an occlusive device such as a balloon or filter to occlude the vessel distal to the obstruction, an optional therapy catheter to treat the obstruction, and a source of aspiration to remove the debris created by the therapy. By utilizing the fluid pressure and flow within the blood vessel, this method eliminates the need for a separate irrigation catheter and irrigation fluid. The present invention allows for the removal of occlusions more rapidly than known methods. Speed is essential in such procedures, since blood flow is significantly decreased or stopped during the time the vessel is occluded. The speed with which normal blood flow is restored is more critical in main vessels which supply blood to collateral vessels. The method of the present invention allows for the removal of occlusions from saphenous vein grafts, coronary arteries, arteries above the aortic arch such as the carotid and cerebral arteries, and blood vessels of similar pressure. The minimally invasive treatment can be provided at low cost and at relatively low risk to the patient.
In accordance with one aspect of the present invention, there is provided a method for the treatment of a stenosis or an occlusion in a blood vessel having a fluid pressure of at least about 0.2 psi. The blood vessel can be a saphenous vein graft, a coronary artery, a blood vessel above the aortic arch, or any other vessel with a fluid flow rate of at least about 10 cc per minute (prior to occlusion of the vessel using an occlusive device as described below), and more preferably, about 60 to 80 cc per minute, or about 120 to 140 cc per minute. This flow rate is needed to provide adequate irrigation fluid, which allows for substantially complete aspiration of the area surrounding the occlusion in a very short period of time. Using this combination of irrigation provided from the blood flow into the vessel and aspiration, it has been found that aspiration of debris and fluid within the working area can occur in less than 3 seconds, but can also continue for 10 to 20 seconds or longer, until the procedure is completed. Thus, the physician can quickly and efficiently clear the debris from the area and restore normal blood flow through the vessel.
One aspect of the method comprises first inserting a catheter or guidewire having an occlusive device at its distal end into the blood vessel, until it is distal to the stenosis or occlusion. It is to be understood that the stenosis or occlusion could be in a discrete location or diffused within the vessel. Therefore, although placement of the occlusive device is said to be distal to the stenosis or occlusion to be treated, portions of the diffuse stenosis or occlusion may remain distal to the occlusive device.
Once in place, the occlusive device is activated to substantially or completely occlude the vessel distal to the existing stenosis or occlusion and to create a working area surrounding the stenosis or occlusion. A therapy catheter is then inserted into the blood vessel until it reaches the stenosis or occlusion, and a desired therapy is performed on the stenosis or occlusion. The fluid inlet pressure within the vessel prevents any particles produced during therapy from flowing against the pressure and out of the working area, thus localizing the particles for aspiration. The therapy catheter is removed, and the distal end of an aspiration catheter or other device which creates an area of turbulence and uses negative pressure to aspirate fluid and debris is delivered into the vessel with the preferred placement being at the working area in a position just proximal to the occlusive device. Fluid is aspirated from the working area inside the vessel preferably proximal to the occlusive device to remove debris, while the fluid pressure within the vessel provides irrigation fluid within the working area. This aspiration creates a fluid flow within the working area, and provides a flow of irrigation fluid into the area. It is this combination of irrigation and aspiration that allows for very fast and efficient removal of debris. Once aspiration is complete, the aspiration catheter or similar device is removed and the occlusive device deactivated. Finally, the catheter or guidewire is removed from the vessel as well.
The insertion can include the act of inserting the proximal end of the guidewire into the hollow lumen inside the aspiration catheter and advancing the aspiration catheter over the guidewire. This is commonly known as xe2x80x9cover-the-wirexe2x80x9d insertion. Alternatively, the proximal end of the guidewire can be inserted into a separate guidewire lumen on the aspiration catheter. Only a short portion of the aspiration catheter, as little as 5 cm, rides over the guidewire as the catheter is advanced. This is known as a single operator system, since, unlike the over-the-wire systems, a second operator is not required to hold the long guidewire while the catheter is inserted into the patient; a single user alone can deliver the catheter over the guidewire in this system.
The distal end of the aspiration catheter or similar device should be slidably inserted into the vessel, across the occlusion and preferably as close to the proximal side of the occlusive device as possible. Thereafter, aspiration is begun and the aspiration catheter should be pulled back by the operator, such that the distal tip slides proximal to the occlusion and the occlusive device. Thus, while the distal tip of the aspiration catheter is preferably initially at a position distal to the occlusion and no more than about 5 cm proximal to the occlusive device, or preferably no more than about 2 cm proximal to the occlusive device, the operator then slides the aspiration catheter back during aspiration, crossing the occlusion and increasing the distance between the distal tip and the occlusive device. Aspiration can therefore occur anywhere between about 0 to 20 cm proximal to the occlusive device. Alternatively, the distal tip of the aspiration catheter may be initially positioned proximal to the occlusion and the occlusive device. Aspiration is begun, and the tip is moved in a distal direction, across the occlusion and immediately adjacent the occlusive device. The tip is then moved in a proximal direction, back across the occlusion. This distal and proximal movement of the catheter tip during aspiration ensures the complete removal of particles and debris from the patient.
The irrigation fluid supplied by the proximal portion of the blood vessel will move any particles or debris from a position proximal to the distal end of the aspiration catheter, thus allowing them to be aspirated. If a particle, however, is too far distal to the tip of the aspiration catheter, the irrigation fluid will tend to keep it there and not allow it to be aspirated from the vessel. The tip of the aspiration catheter can therefore be slidably advanced in a distal direction more than once if desired, to ensure complete removal of debris. Once aspiration has begun, additional blood will flow into the area, creating turbulence and also allowing for the removal of debris.
If desired, a guide catheter can first be inserted into the patient""s body to aid in the insertion of the guidewire and catheters. The guide catheter can be used to provide aspiration in place of the aspiration catheter if desired. The guide catheter is then removed following completion of the procedure.
In accordance with another aspect of the present invention, there is provided a method for the treatment of a stenosis or an occlusion in a blood vessel having a fluid pressure of at least about 0.2 psi, and a fluid flow rate of at least about 10 cc per minute (when not occluded using an occlusive device as described), and more preferably, about 60 to 80 cc per minute, or 120-140 cc per minute. The method comprises the steps of inserting a guidewire or catheter having an occlusive device on its distal end into the blood vessel, until the occlusive device is distal to the stenosis or occlusion. The occlusive device is activated to substantially occlude the vessel distal to the existing stenosis or occlusion and create a working area surrounding the stenosis or occlusion. A therapy catheter is then inserted into the lumen of an aspiration catheter or similar device, and the therapy catheter and the aspiration catheter are simultaneously delivered into the blood vessel until they reach the stenosis or occlusion. Therapy is performed to eliminate the occlusion, and the fluid pressure within the vessel acts to prevent any particles produced during therapy from flowing against the pressure and out of the working area. When therapy is complete, the therapy catheter is removed while the aspiration catheter remains, and fluid inside the working area is aspirated to remove the particles while the fluid pressure provides irrigation fluid within the working area. When aspiration is complete, the aspiration catheter or similar device is removed and the occlusive device is deactivated. The guidewire or catheter is also then removed.
In accordance with yet another aspect of the present invention, there is provided a method for the treatment of a stenosis or an occlusion in a blood vessel having a fluid pressure of at least about 0.2 psi, and a fluid flow rate of at least about 10 cc per minute (prior to occlusion using an occlusive device). The method comprises inserting an occlusive device into the vessel until the occlusive device is distal to the stenosis or occlusion. The device can be attached to the distal end of a catheter or guidewire. The device is actuated to occlude the vessels distal to the existing stenosis or occlusion and create a working area surrounding the stenosis or occlusion. The fluid pressure within the vessel prevents any particles dislodged during insertion of the guidewire or catheter from flowing against the pressure and out of the working area. The distal end of an aspiration catheter or similar device is inserted to a position just proximal to the occlusive device, and fluid from the working area inside the vessel just proximal the occlusive device is aspirated. This will remove the stenosis or occlusion and any free particles while the fluid pressure provides irrigation fluid within the area. When aspiration is complete, the aspiration catheter is removed and the occlusive device deactivated. The guidewire or catheter is then removed.
Another aspect of the present invention involves the use of an expandable device, such as an inflatable balloon, to inhibit the migration of emboli or other particles in a proximal to distal direction within the vessel. This can be done by at least partially occluding the vessel at a site distal to the emboli or other occlusion. Again, although placement of the expandable device is said to be distal to the emboli or other occlusion to be treated, in the case of a diffuse occlusion, outlying portions of the occlusion may remain distal to the device.
The fluid pressure within the vessel prevents emboli or other particles from migrating in a distal to proximal direction. If desired, a therapy catheter may be used to perform therapy on the vessel at the site of the emboli or occlusion. The therapy catheter may be removed, and a catheter, such as an aspiration catheter, having a lumen in fluid communication with a distal opening in the catheter is advanced across the site of the emboli or occlusion such that the opening is distal to at least a portion of the emboli or occlusion. Fluid is then drawn through the distal opening in the catheter to remove the emboli, occlusion or debris. By drawing fluid into the opening, a fluid flow is created in the lumen of the catheter in a distal to proximal direction, while simultaneously, fluid flows in a proximal to distal direction in the vessel.
In accordance with yet another aspect of the invention, there is provided a method for the evacuation of emboli from a blood vessel. A catheter having a lumen in fluid communication with a distal opening in the catheter is positioned such that the opening is distal to at least a portion of an occlusive substance, such as emboli, within the blood vessel. Fluid is then drawn from the vessel into the distal opening such that the emboli are carried from the vessel into the distal opening and through the lumen of the catheter. The fluid intake preferably simultaneously creates a fluid flow in the lumen in a distal to proximal direction, and in the vessel in a proximal to distal direction. During the fluid intake through the catheter, the distal opening in the catheter is preferably moved from a position distal to the occlusive substance, to a position proximal to the occlusive substance, to a position distal to the occlusive substance to ensure complete removal of particles.
Accordingly, the present invention provides for very fast and efficient aspiration of an area surrounding an occlusion in a blood vessel. The patient""s own blood provides the irrigation fluid, thereby eliminating the need for a separate irrigation catheter and supply of irrigation fluid. By reducing the number of devices needed to be inserted into the patient, the present invention reduces the amount of time required to complete the procedure, and allows the physician to restore normal blood flow in the vessel in a very short period of time.